The invention relates to a clamping fixture for axially clamping a tool in place in particular a disc and comprising a clamping nut to be screwed on a threaded end of a spindle, and a clamping member arranged between the nut and the spindle. Clamping fixtures of this type are suitable in particular for portable power hand tools and in this respect particularly for grinding machines, for example. A clamping fixture of the said type has been disclosed (German Pat. No. Spec. 3,012,836) in which the clamping member consists of an element which is roughly pot-shaped in cross-section and is axially supported on the clamping nut via a helical spring. When the clamping nut is screwed on and tightened, the hat-shaped clamping member is pressed axially against the tool via the axially compressed spring, and the tool is thereby tightened against the flange on the spindle side, the end face of a cylindrical sleeve extension of the clamping nut bearing directly on a facing axial side of the flange on the spindle side and, during further tightening of the clamping nut, the flange on the spindle side being tightened together with the clamping nut. This is to ensure in an angle grinder that the grinding disc is mounted with a predetermined contact pressure and that this contact pressure remains at the right level. The clamping fixture is also intended to permit a quick and simple interchange of the grinding disc and, at the same, time avoid overloading of the power hand tool, in particular the angle grinder. This is because, if the torque acting on the grinding disc is too great, the grinding disc stops, while the flange on the spindle side and also the clamping nut having the clamping member perform a relative movement thereto. The effect of the clamping nut automatically being tightened further in operation, makes it considerably more difficult to loosen the clamping nut, when changing the grinding disc, in this clamping fixture. Therefore, loosening of the clamping nut is here only possible with assistance of a special auxiliary tool, the spindle, depending on the design of the machine, having to be appropriately counterheld by a second auxiliary tool, e.g. a spanner.